1. Field of the Invention
The present invention relates to an antenna matching apparatus.
2. Description of the Related Art
Mobile communication terminals supporting multiple frequency bands (multiband mobile communication terminals) have hitherto been in practical use. The multiple frequency bands are composed of, for example, a combination of a relatively low frequency band (low band) and a relatively high frequency band (high band). Excellent transmission-reception characteristics are required of the mobile communication terminals in both the low band and the high band.
Japanese Unexamined Patent Application Publication No. 2006-246070 discloses an antenna element having a configuration in which a matching circuit is capable of being switched. With this configuration, the antenna element is matched with any of multiple bands.
Japanese Unexamined Patent Application Publication No. 2008-160226 discloses a reception apparatus matched with any of multiple bands. This reception apparatus adjusts the impedance of a matching circuit in accordance with a variation in impedance of an antenna.
Technologies have been developed in recent years in which transmission and/or reception is performed by simultaneously using multiple frequency bands to improve the communication speeds of mobile communication terminals. Such technologies are exemplified by a technology called carrier aggregation defined in Long Term Evolution (LTE) (Registered Trademark) Advanced standard. Such technologies are simply referred to as “carrier aggregation” in the following description. In the carrier aggregation, the respective bands, for example, the low band and the high band are simultaneously used.
The antenna element described in Japanese Unexamined Patent Application Publication No. 2006-246070 and the reception apparatus described in Japanese Unexamined Patent Application Publication No. 2008-160226 are each configured so as to appropriately adjust the matching circuit for one band, among the respective multiple bands. When the matching circuit is adjusted for one band in the carrier aggregation, the matching is not appropriately performed for the other bands. As a result, since the transmission-reception characteristics and so on in the other bands are reduced, the communication performance achieved by the carrier aggregation is degraded.